Abstract: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibodies to nuclear components in the cell. Despite decades of extensive work in the understanding of the etiopathogenesis of SLE, there has not been a specific biomarker shown to indicate disease pathogenesis. Additionally, extensive analysis of both genetics and environmental pathogens has yet to reveal a common mechanism for the initiation of disease. The recent discovery of microRNAs (miRNAs) has initiated a flurry of investigations into how miRNA may regulate gene expression. Substantial evidence exists that the miRNA system contributes to the regulation of a wide variety of normal cellular functions and pathologies. Microarray data has shown that miRNA expression in peripheral blood cells of SLE patients is altered compared to healthy controls. We have recently demonstrated the importance of miRNA in immune cells and have shown the selective regulation of miRNA expression in immune cells by estrogen. Given the role of miRNA in the regulation of inflammation, we hypothesize that mesangial cells from NZB/W female mice will show an altered miRNA profile in the initiation and progression of glomerulonephritis. To test our hypothesis we propose the following Specific Aim: Specific Aim 1: Define the expression profile of miRNA in mesangial cells from NZB/W female mice as they age. While it is clear that miRNA plays a critical role in the regulation of cellular differentiation, hematopoesis, and the regulation of the immune system, the relevance of altered miRNA expression patterns and its role in SLE is unclear. Mesangial cells play a critical role in the pathogenesis of lupus nephritis. The completion of these experiments will yield important insight of the molecular workings of mesangial cells. Our studies will: 1. Determine if miRNA expression from freshly purified mesangial cells from NZB/W mice correlates or predicts the development of disease progression. 2. Correlate the changes in miRNA expression to pathological changes in the kidney to detail how miRNA expression parallels disease activity. 3. Seek to establish a role for altered miRNA expression in lupus and thus shift the paradigm in our understanding of how SLE disease is initiated. 4. Determine if miRNA expression profiles can be used as a biomarker for disease activity. 5. Provide evidence to develop novel approaches for the targeting disease by manipulating miRNA expression in cells. PUBLIC HEALTH RELEVANCE: Extensive analysis of both genetics and environmental pathogens of systemic lupus erythematosus (SLE) has yet to reveal a common mechanism for the initiation of disease. The recent discovery of microRNAs (miRNAs) which are short noncoding RNA molecules that inhibit gene expression through incomplete base pairing with the 30- untranslated region (30-UTR) of target mRNAs have initiated a flurry of investigations into how miRNA may regulate gene expression. We have recently demonstrated the importance of miRNA in immune cells and have shown the selective regulation of miRNA expression in immune cells by estrogen. Given the role of miRNA in the regulation of inflammation, we hypothesize altered miRNA expression in mesangial cells from NZB/W female mice with undergo alterations of expression that can be measured to identify the initiation and progression of glomerulonephritis. To test our hypothesis, we propose to define the expression profile of miRNA in mesangial cells from NZB/W female mice as they age. The completion of these experiments will yield important insight of the molecular workings of mesangial cells. Our studies will examine the miRNA expression from freshly purified mesangial cells and we will detail alterations of miRNA with disease progression. We will correlate the changes in miRNA expression to pathological changes in the kidney to detail how miRNA expression parallels disease activity. If we can establish a role for altered miRNA expression in lupus, these studies will shift the paradigm in our understanding of how SLE disease is initiated.